My brothers told me not to watch either Munich or Syriana unless I wanted to kill something, and I trust me brothers when they say that, so I'll hold off on that. As for "Zulu," I belive the answer comes down to at most, once a month if you don't want to start overanalising it as some people are prone to doing...
As for my favorite all-time favorite, I have to say "Soldier of Orange."